1. Field of the Invention
The present invention relates to a device for stapling sheets arranged in stacks, which comprises a driver unit for driving the staples from one side and a clincher unit for folding over the staple ends from the other side, both units being actuated by a rotary control member, and which also comprises a slider that connects the clincher unit with a cam of the control member.
2. Description Relative to the Prior Art
U S. Pat. No. 4,557,410 discloses a device of this type wherein the staples are driven by a rotating cam disk to which a bellcrank hinged to the driver unit is eccentrically mounted. The back-up for the sheets to be stapled is stationarily arranged in the housing. In the case of this known device, a force of varying strength is required for the driving operation, which must be greatest in the most unfavorable position of the crank pin on the side of the cam disk, i.e. at the point when the staple penetrates the sheets. This causes a bearing load, which is one-sided and which varies, on the cam disk and on the crank pins. Apart from the fact that the bellcrank with its crank pins requires additional control and increases noise, the bearing sites of such parts, and in particular, the bearing means of the cam disk have to be stable enough to withstand the high one-sided bearing pressures which are, moreover variable Such a device cannot, therefore, be manufactured from inexpensive materials.